Detection system for autofocus function of image capture device and control method thereof

ABSTRACT

A detection system for an image capture device includes an image detecting unit, a calculation unit, a selection unit and a switching unit. The image detecting unit provides a plurality of focus modes suitable for different ambient light conditions, and acquires image parameters. The calculation unit determines exposure time suitable for the current ambient light conditions based on the acquired parameters. The selection unit selects a suitable detection mode based on the determined exposure time. The switching unit switches the image capture device to the selected suitable detection mode.

BACKGROUND

1. Technical Field

The disclosure relates to a detection system for an autofocus function of an image capture device and a control method thereof.

2. Description of the Related Art

Image capture devices such as digital still cameras and digital video cameras utilize various detection systems when acquiring images. Image quality is influenced by detection modes of the systems, normally preset by manufacturers. When acquiring images, a suitable detection mode is selected according to current parameters of the target image. Such selection is inconvenient and typically requires expert skills.

Therefore, it is desirable to provide a detection system for an autofocus function of an image capture device and a control method which can overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the disclosure can be better understood with reference to the drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the detection system for the autofocus function of the image capture device and the control method thereof. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a block diagram of a detection system, according to an embodiment of the disclosure.

FIG. 2 is a flowchart of a control method for a detection system according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the detection system for the autofocus function of an image capture device and control method thereof are described in detail here with reference to the drawings.

As shown in FIG. 1, a detection system 100 is applied in an image capture device 200 such as a digital still camera, and includes a detection unit 110 and a control unit 120 electrically coupled to the detection unit 110.

The detection unit 110 provides a plurality of detection modes and is configured to acquire image parameters. For example, the detection unit 110 can be a charge-coupled device (CCD) sensor.

The detection unit 110 provides parameters affecting an autofocus function of the image capture device 200, such as resolution, frame rate, and light sensitivity, where resolution represents scan lines of the detection unit 110; frame rate represents the measurement of the frequency expressed in frames per second (fps); and light sensitivity represents efficiency of conversion from light into electric signals to form image signals.

In this embodiment, the detection modes include a first detection mode, a second detection mode, and a third detection mode. In each of the detection modes, a corresponding exposure time Tv value is used in a focus function of the image capture device 200. For example, in the first detection mode, the detection unit 110 may provide a 3264×272 resolution, a frame rate ranging from 30 to 60 fps, and a low level light sensitivity. In the second detection mode, the detection unit 110 may provide a 1088×816 resolution, a 30 fps frame rate, and a high level light sensitivity. In the third mode, the detection unit 110 may provide a 1088×272 resolution, a 60 fps frame rate, and a medium level light sensitivity. As mentioned, each group of these three parameters: resolution, frame rate, and light sensitivity constitutes a setting of the autofocus function of the image capture device 200.

The detection modes are selected based upon an exposure time value Tv, determined to be suitable for current ambient light conditions. For example, when the ambient light condition is brighter, a shorter Tv is determined to be adopted to avoid overexposure and accordingly the third detection mode wherein high frame rate (allowed by the shorter Tv) is selected for increasing focus velocity. In other words, when the ambient light condition is darker, a longer Tv is determined to be suitable to obtain adequate exposure and accordingly the second detection mode, with high light sensitivity, is selected to achieve adequate exposure.

The control unit 120 includes a calculation unit 122, a selection unit 124 and a switching unit 126.

The calculation unit 122 is configured to determine the Tv suitable for the current ambient light conditions using the formula:

Av+Tv=Bv+Sv

wherein Av represents an aperture value, Sv represents an automatic gain control (Agc) value, and Bv represents brightness. In detail, the Av and Sv are read from the image capture device 200, and the Bv is provided from the detection unit 110.

The selection unit 124 selects an appropriate detection mode based on the determined Tv.

The switching unit 126 switches the detection unit 110 to the selected detection mode.

FIG. 2 shows a control method based on an embodiment which may be performed by, for example, a detection system 100 of FIG. 1.

In step 201, image parameters are acquired by a detection unit 110. The detection unit 110 provides first, second, and third detection modes, each suitable for different ambient conditions.

In step 202, the Tv value is determined. The determination is performed by a calculation unit 122 based on Av, Sv and Bv values.

In step 203, whether the Tv value is less than 60 fps is determined. If not, step 204 is employed. If the Tv value does not exceed 60 fps, step 205 is employed.

In step 204, the third detection mode is selected, in which frame rate equals 60 fps.

In step 205, whether the Tv value exceeds 30 fps is determined. If so, step 207 is employed. If not, step 206 is employed.

In step 206, the first detection mode is selected, in which the frame rate is from 30 to 60 fps.

In step 207, the second detection mode is selected, in which frame rate equals 30 fps.

The detection system 100 automatically detects Tv value and switches the image capture device 200 to a corresponding suitable detection mode according to the ambient light conditions for autofocus. It is convenient for automatically detecting the Tv value and switching the image capture device 200 for autofocus to the suitable detection mode without manual determination.

While the disclosure has been described by way of example and in terms of preferred embodiment, it is to be understood that the disclosure is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements. 

1. A detection system for an autofocus function of an image capture device, comprising: a detection unit providing a plurality of detection modes suitable for different ambient light conditions, and capable of acquiring image parameters; a calculation unit capable of determining exposure time suitable for the current ambient light conditions based on the acquired image parameters; a selection unit capable of selecting a suitable detection mode based on the determined exposure time; and a switching unit capable of switching the image capture device to the selected suitable detection mode.
 2. The detection system of claim 1, wherein the determination of the exposure time is based on the formula: Av+Tv=Bv+Sv wherein Av represents an aperture value, Tv the exposure time, Bv brightness value, and Sv an automatic gain control value.
 3. The detection system of claim 1, wherein each of the plurality of detection modes comprises different parameters comprising resolution, frame rate, and light sensitivity.
 4. The detection system of claim 3, wherein the plurality of detection modes comprises: a first detection mode using resolution of 3264 by 272, frame rate of 30 to 60 fps, and light sensitivity low; a second detection mode using resolution of 1088 by 816, frame rate of 30 to 60 fps, and light sensitivity high; and a third detection mode using resolution of 1088 by 272, frame rate of 60 fps, and light sensitivity medium.
 5. A control method for a detection system applied to an image capture device, comprising: acquiring image parameters; calculating exposure time suitable for ambient light conditions based on the acquired image parameters; determining whether the exposure time exceeds a first predetermined value; and switching the image capture device to a first detection mode if the exposure time does not exceeds the first predetermined value.
 6. The control method of claim 5, further comprising determining whether the exposure time exceeds a second predetermined value if the exposure time exceeds the first predetermined value.
 7. The control method of claim 6, further comprising switching the image capture device to a second detection mode if the exposure time exceeds the second predetermined value.
 8. The control method of claim 6, further comprising switching to a third detection mode if the exposure time does not exceed the second predetermined value.
 9. A control method for a detection system, comprising: providing an image capture device containing the detection system capable of providing a plurality of detection modes suitable for different ambient light conditions; acquiring image parameters; calculating exposure time suitable for ambient light conditions based on the acquired image parameters; determining whether the exposure time exceeds a first predetermined value; and switching the image capture device to a first detection mode if the exposure time does not exceed the first predetermined value.
 10. The control method of claim 9, further comprising determining whether the exposure time exceeds a second predetermined value if the exposure time exceeds the first predetermined value.
 11. The control method of claim 10, further comprising switching the image capture device to a second detection mode if the exposure time exceeds the second predetermined value.
 12. The control method of claim 10, further comprising switching to a third detection mode if the exposure time does not exceed the second predetermined value. 